pgsuper design guide - texas department of … · pgsuper design guide ... lrfd bridge design...

PGSuper Design Guide

July 2015


July 2015 TxDOT 2

Table of Contents

1 Some Common Questions ..................................................................... 3

2 Basic Design with PGSuper .................................................................. 3

3 Additional Features in PGSuper .......................................................... 4

3.1 Terminology ......................................................................................................... 4

3.2 Horizontal Curves, Vertical Curves, and Cross-Slope ......................................... 4 3.3 Bridge Geometry, Beam Type, and Beam Spacing ............................................. 5

3.4 Beam Design and Modification............................................................................ 6 3.5 Project Controls .................................................................................................... 7 3.6 Loads .................................................................................................................... 8

3.6.1 User Defined Loads ...................................................................................... 8

3.6.2 Live Loads .................................................................................................... 8 3.6.3 Live Load Distribution Factors ..................................................................... 9

3.7 Modeling Inverted T’s ........................................................................................ 10

4 TOGA .................................................................................................... 11

5 Additional Information and Questions .............................................. 12

Appendix A .................................................................................................. 13

STEP 1 - OPEN TEMPLATE .................................................................................... 16

STEP 2 - INPUT BEAM SPACING AND NUMBER OF BEAMS ....................... 18

STEP 3 - INPUT SPAN LENGTH AND SKEW ..................................................... 20 STEP 4 - INPUT DECK WIDTH .............................................................................. 24 STEP 5 - RUN THE DESIGN ALGORITHM ......................................................... 26

STEP 6 - OUTPUT THE SUMMARY REPORT .................................................... 30

STEP 7 - OUTPUT THE TEXT DATA FOR THE DETAIL SHEET (IBND,

IGND, ETC.)................................................................................................................ 36

Appendix B .................................................................................................. 41

METHOD FOR DEVELOPING NON STANDARD STRAND PATTERN ........ 42


July 2015 TxDOT 3

1 Some Common Questions

“Why PGSuper?”

PGSuper is a windows bases application to design prestressed concrete beams to

the current LRFD specifications. The program

Calculates Loads (Rail and Overlay)

Calculates Live Load Distribution Factors (No more spreadsheets)

Designs ANY Beam in a cross section.

“Doesn’t PGSuper require a lot more input and take more time that PSTRS14?”

No, though the program has the ability to model very complex structures, you do

not have to use all the program features to reach a beam design. You just need to input

the span length, skew, beam spacing, number of beams, and deck width.

“Do we still need PSTRS14?”

PSTRS14 will still be needed for those rare occasions when we are designing or

analyzing to the Standard Specification or to the AREMA Specifications.

“Which should I use?”

PGSuper should become your primary tool for beam design for AASHTO LRFD.

You can use PSTRS14 to confirm your PGSuper designs. The two programs should

result in the same beam design. If they do not, verify that input is matching between the

two programs.

2 Basic Design with PGSuper

The steps to design a beam in PGSuper can be simplified to

1. Open a Template for the appropriate beam type.

2. Input Beam Spacing and Number of Beams.

3. Input Span Length and Skew.

4. Input Deck Width.

5. Run the Preliminary Girder Designer.

6. Verify design meets requirements (i.e. f’ci < 6.0 ksi; f’c < 8.5 ksi).

7. Run the TxDOT Summary Report.

8. Export the Text Data for the Detail Sheet (IBND, IGND, etc.).

These steps are detailed in the design example presented in Appendix A.


July 2015 TxDOT 4

3 Additional Features in PGSuper

PGSuper has the ability to model geometrically complex bridges, such as, flared or

tapered beams, varying slab widths, and sidewalks. The following sections cover some

of these features and the TxDOT Method associated with that feature. This is not a

comprehensive guide on how to use every aspect of PGSuper, just a brief introduction to

some of the features in PGSuper.

Additional information can be found in the Help menu.

Additional tutorials can be found online at http://www.pgsuper.com/

3.1 Terminology

PGSuper uses the following terminology to determine when to apply loads.

Casting Yard Stage – The loads modeled in this stage are the girder self

weight and prestressing forces.

Bridge Site Stage 1 – The loads are applied to the non composite section.

These loads include the slab, diaphragms, and shear keys.

Bridge Site Stage 2 – The loads are applied to the short-term composite

section. These loads include railing systems, sidewalks, medians,

and overlays.

Bridge Site Stage 3 – The loads are applied to the long-term composite

section. These loads include future overlay load, live load, and

pedestrian live load.

3.2 Horizontal Curves, Vertical Curves, and Cross-Slope

Commands – Edit: Alignment or Click on .

Horizontal – Under this tab you can model the horizontal curves.

Profile – PGSuper has the capability of modeling vertical curves. However, due to the

way PGSuper treats the additional concrete due to a curve, TXDOT has decided NOT to

use this feature.

Superelevations – PGSuper can model the cross slope of a bridge. However, the program

assumes the cross slope is constant on either side of the crown point. In other words, you

can only model one (1) cross slope break.

http://www.pgsuper.com/


July 2015 TxDOT 5

3.3 Bridge Geometry, Beam Type, and Beam Spacing

Command – Edit: Bridge or Click .

Bridge Line vs. Alignment – In PGSuper, the Bridge Line defaults at the center of the

beams. In addition, the Alignment defaults to be along the Bridge Line. You change the

location of the girders relative to the Bridge Line or the Alignment under the General

Tab. You can offset the Alignment relative to the Bridge Line on the Framing Tab.

General – Under the General tab, if “Use same type for all girders” is unchecked, if “Use

same number of girders in all spans” is unchecked, or if Spacing Type is set to “Spread

girders with unique spacing for each span”, then the Girder Type and Spacing may be

modified through the Framing Tab: Edit Abutment Details or Edit Span Details.

Framing – This section is where you set the abutment and bent locations and skews. In

addition, by clicking the Edit Abutment or Span Details button you can modify the span

length, beam connection type, and the girder type and spacing. Girder type and spacing

can only be modified if the settings under the General tab meet certain requirements as

discussed above.

Railing System – Drop downs allow you to select any of the standard TxDOT Bridge

Rails. In addition, you can model sidewalks here. Sidewalk modeling will be discussed

in a later section.

Deck Geometry and Materials – In this area, you define the width and depth of the bridge

slab.

“Gross Depth” defaults to 8.5”.

The “Slab Offset” is the slab plus haunch value. Due to the way PGSuper models the

haunch concrete, TxDOT has chosen NOT to use this feature. Haunch should be set to

zero at this point and the “Slab Offset” should match the “Gross Depth. The load due to

the haunch concrete can be modeled as a User Defined Load, as discussed in later

sections.

Deck Reinforcement – The deck reinforcement had been set to a default value. This tab

does not impact the design of the beam and can be ignored.

Condition and Rating – TxDOT has NOT approved PGSuper as a load rating tool. Ignore

this entry tab.


July 2015 TxDOT 6

3.4 Beam Design and Modification

As discussed previously, you can do a preliminary design of a beam using the Girder

Designer. In addition, you can design a girder or modify a given design using the “Edit a

Girder” feature of PGSuper.

Command – Edit: Girder or Click . Then select the Girder you wish to edit.

Long. Reinforcement and Trans. Reinforcement – Under these tabs you can modify the

secondary reinforcement in the beam. These values default to the secondary

reinforcement shown on TxDOT’s Standard Drawings. If you have to modify any of

these values for any reason, the Standard Drawing will have to be modified to match your

design. We recommend NOT changing these values, unless you absolutely have to, to

meet shear requirements.

Per the memorandum, titled Design Release Strengths for Prestressed Concrete Beams,

dated August 26, 2010, “Bridge design engineers will use the .65 design release factor in

the design of all prestressed concrete beams on project designed after October 1, 2010, in

place of the existing .60 factor.” and “Designers will target 5,500 as their design release

strength maximum. Under extreme circumstances where spans length or beam spacing

cannot be reduced for reasons of practicality, design release strengths shall not exceed

6,000 psi.”

What are your options when your release strength exceeds 5,500 psi?

1.) Use a deeper beam section (i.e. Tx46 instead of a Tx40)

What if, the vertical clearance prohibits the use of a deeper beam section?

2.) Reduce Span Length

What if, to clear the river, lower roadway or railroad the span length is at the

minimum it can go?

3.) Reduce Beam Spacing. If the beam spacing is less than 6 feet, we recommend

reducing the overhang width to S/2 or less. As a general guideline, the overhang

should not be less than 2 feet.

What if, my beam spacing is less than 4 feet and my release strength is still high?

4.) Use a non standard strand pattern. The Edit: Girder feature in PGSuper allows

you to manually change the strand pattern to reach a lower release strength. This

procedure is shown in Appendix B.


July 2015 TxDOT 7

3.5 Project Controls

In the main toolbar, the Project Tab, these items have been set to default TxDOT values

as shown below.

Units – Customary U.S. Units

Structural Analysis Method – Simple Span Analysis

Project Criteria – TxDOT YEAR. The year will reflect the latest AASHTO LRFD Bridge

Design Specification that TxDOT has adopted, i.e. TxDOT 2010 refers to the AASHTO

LRFD Bridge Design Specification, Fifth Edition, 2010 with modifications for TxDOT

policy as outlined in the Bridge Design Manual. If a pure AASHTO LRFD design

method is desired, change this selection to LRFD YEAR.

The TxDOT 2010 and later project criterion defaults to the 0.65 release factor per the

memorandum, titled Design Release Strengths for Prestressed Concrete Beams, dated

August 26, 2010.

Load Rating Options – TxDOT has NOT adopted PGSuper as a load rating tool. Ignore

this section and any others dealing with load rating.

Properties – This field brings up the initial “Project Properties” screen that appears when

you first open a new template in PGSuper. The information in this section includes the

Bridge Name, Bridge ID, Job Number, Engineer Name, Company, and Comments.


July 2015 TxDOT 8

3.6 Loads

3.6.1 User Defined Loads

You can model additional loads, such as medians, light poles, signs, and haunch through

the use of user defined loads.

When defining a load, the available load cases are DC (dead load, component), DW

(dead load, wearing surface), and LL+IM (live load plus impact). For the DC and DW

cases, the available stages are Bridge Site 1 and Bridge Site 2. The LL+IM load can only

be applied to the Bridge Site Stage 3.

Discrete objects just as light poles or signs should be modeled using the “Add New Point

Load” feature. The load case would be DC, the Stage would be Bridge Site 2.

PGSuper assumes the rail and sidewalk are located at the edge of the slab. In addition,

PGSuper distributes the rail, sidewalk, and pedestrian live loads to the exterior 3 beams.

Unless you are modeling U beams then 2/3 of the rail weight is applied to the exterior

beam and 1/3 to the first interior beam. If you want to distribute the load differently, you

can set the rail to “none” and not model a sidewalk, the loads can then be modeled using

“User Defined Loads”, specifically the “Add Distributed Load” feature.

3.6.2 Live Loads

The program allows you to select which truck you would like to design for Service and

Strength Limit States, Fatigue Limit State, and Permit Limit States. The default settings

are HL-93, the Fatigue truck, and nothing, respectively.

Sidewalk Loads -If you model a sidewalk, PGSuper will automatically turn on the

Pedestrian on Sidewalk load. PGSuper applies the sidewalk live load concurrently with

the vehicular live load. You can turn off the pedestrian live load by unchecking the box

beside the load case.

Engineering judgment and experience should be used to determine if the beam should be

designed for concurrent vehicular and pedestrian live load, vehicular only, or pedestrian

only.

PGSuper distributes the pedestrian live load in the same manner that the sidewalk and rail

are distributed, which follows the TxDOT Bridge Design Manual. The load is divided

over the three exterior beams

To model the sidewalk and pedestrian load differently than the PGSuper default.


July 2015 TxDOT 9

Do not define a sidewalk. The program will apply the vehicular load to all the

beams.

Define a User Define Distributed Load to distribute the sidewalk dead load. (DC,

Bridge Site 2).

Define a User Defined Distributed Load to distribute pedestrian live load

(LL+IM).

3.6.3 Live Load Distribution Factors

The program defaults to calculating the live load distribution factors using the AASHTO

LRFD Bridge Design Specification with modifications for TxDOT policy as outlined in

the Bridge Design Manual.

Occasionally, a bridge will fall outside the ranges of applicability as designed by the

ASSHTO Specifications. In these cases, when you go to run the Preliminary Girder

Designer, the program will give you the warning “Live Load Distribution Factors could

not be calculated for the following reason xxxxx. See Table 4.6.2.2.2b-1. A refined

method of analysis in required for this bridge. See Status Center for Details.”

The status center can be accesses by clicking on the Red X or the Yellow !. When you

click on the error message in the status center, the program opens the Refined Analysis

Options dialogue.


July 2015 TxDOT 10

How do you decide which option you should select?

This issue comes down to engineering judgment and experience. Some guidelines are as

follows.

If all the parameters are within the ROA, use the value as calculated by PGSuper.

If the ROA are violated by a great amount, use the lever rule. An example of this

would be S = 20 feet, when the range is 3.5 to 16 feet.

Within a small violation of the ROA, it would probably be acceptable to ignore

the ROA. An example of this would be a t=4", when the range is 4.5 to 12 inches.

The Ranges of Applicability (ROA) found in Section 4.6.2.2 reflect the limits of

the research that was done to investigate distribution factors. The ROA's do not

necessarily indicate the range for which the formulas are valid; rather they reflect

the limits of what was studied in the development of the formulas.

When a design falls outside the ROA it is left up to the engineer's judgment to

decide to apply the formulas or determine the live load distribution factor by some

other method. One way to help make that judgment would be to do a simple

sensitivity study using the value that is outside the ROA.

You can modify the Live Load Distribution factors at any time through Project: Live

Load Distribution Factors. The dialogue that appears offers the same options as shown

above.

3.7 Modeling Inverted T’s

In order to model an inverted T in PGSuper, you have to create a connection in the

library. The steps to modify a beam connection are as follows.

1.) Select "Library" from the toolbar at the top.

2.) Select "Edit Libraries".

3.) From list on left of screen, double click on "Connections". A listing of the

preset connections will be shown in the screen on the right.

4.) Click on the one the one that matches the right beam time if you ignore the

stem. Right click, select "Duplicate".

5.) Double Click the copied connection, title will be "the original title (Copy

1)".


July 2015 TxDOT 11

6.) Right Click, select "Rename". Change to a name you will remember (ie.

Inverted T Bent 2.)

7.) Double Click to open the Connection dialog.

8.) Modify the "End Distance" and "Bearing Offset" by increasing by half the

Stem Width. End distance is the distance from the centerline of the bearing

to the end of the girder. Bearing offset is the distance from the centerline

bent to the centerline of bearing. The difference in these two numbers is the

value typically shown on our plans (ie. 3".) The diagram on the left side

displays these values.

9.) Side note - Measure End Distance and Bearing Offset is always "Normal to

Abutment/Pier" for Inverted Ts.

10.) Click "Ok" to exit the dialog, "X" out of the library editor. You can now go

to the "Bridge Description" dialog and select the connection you just created

on the "Piers" tab, "Connection Geometry".

Final note: Changes to the library in this manner will be specific to the project (file) you

are working on and will not transfer over when you create a new file from the templates.

4 TOGA

TxDOT has developed an Optional Girder Analysis plug-in for PGSuper. This plug-in is

called TxDOT Optional Girder Analysis (TOGA). You can access TOGA through File>

New. At the bottom of the dialogue under “TxDOT Option Girder Analysis” select

“Templates”. Then select the girder type you are analyzing. For additional instructions in

using TOGA, when you are in TOGA select Help: Help Topics. In the Help Topic, is a

very comprehensive guide to the use of TOGA.


July 2015 TxDOT 12

5 Additional Information and Questions

Additional information can be found in the

PGSuper Help menu.

TOGA Help menu

Additional tutorials can be found online at


Questions or technical support contact the Bridge Division

[email protected]



July 2015 TxDOT 13

Appendix A


July 2015 TxDOT 14


July 2015 TxDOT 15


July 2015 TxDOT 16

STEP 1 - OPEN TEMPLATE


July 2015 TxDOT 17

Bridge Name

Bridge ID

CSJ Your Name

Any Additional

Information

Fill in Fields and

then Click OK


July 2015 TxDOT 18

STEP 2 - INPUT BEAM SPACING AND NUMBER OF BEAMS

Click here or Edit: Bridge


July 2015 TxDOT 19

Input Number of Beams

Input Beam Spacing


July 2015 TxDOT 20

STEP 3 - INPUT SPAN LENGTH AND SKEW

Click here

Then Click here


July 2015 TxDOT 21

Input Span Lengths


July 2015 TxDOT 22

Input Skew Table is automatically

updated based on what is

input on the “Layout by

Span Lengths


July 2015 TxDOT 23

Default rail settings. Do

not change unless you are

using a heavier rail.


July 2015 TxDOT 24

STEP 4 - INPUT DECK WIDTH

Click here

Input slab width, half of overall width in each field.

Click OK

Default setting of 2 inches of future overlay.


July 2015 TxDOT 25

The program automatically updates the Plan and

Elevation views to reflect the inputted information.


July 2015 TxDOT 26

STEP 5 - RUN THE DESIGN ALGORITHM

Move the Section View Bar

by Dragging and Dropping to

be all on one span.

Click once on the beam

you want to design.


July 2015 TxDOT 27

Click here or Project: Design Girder

Defaults to the Span and

Beam you selected or you

can use the dropdown

arrows to change to a

different span and beam.

Design for Flexure ONLY.

Do NOT design for Shear.

The default stirrup spacing

is based on the standard

beam and should not be

changed unless there is a

structural need. Click Run Design to start

the design algorithm.


July 2015 TxDOT 28

The design algorithm is

running.


July 2015 TxDOT 29


July 2015 TxDOT 30

STEP 6 - OUTPUT THE SUMMARY REPORT

Click here or View: Reports

Select the “TxDOT

Summary Report” or

“TxDOT Girder

Schedule Report.”

The TxDOT

Summary Report

includes the Girder

Design, Camber,

Deflections, and the

Specification

Checks.

The TxDOT Girder

Schedule Report

includes the Girder

Design, Camber,

and Deflections,

only.


July 2015 TxDOT 31







July 2015 TxDOT 32

The report is processing.


July 2015 TxDOT 33

The report is ready. This

is the first page.


July 2015 TxDOT 34

The following are only

portions of the report.

Confirm the design is valid by checking if the

Specification Check was successful in this section

The Girder Summary Section provides the Beam Design.

Use the circled values for determining Haunch.

The deflection circled is the Pnt B

(1/2) deflection. To calculate the Pnt

A (1/4) deflection multiply Pnt B by

0.7123.

For this example

Pnt B = -0.093 ft.

Pnt A = 0.7123(-0.093) = -0.066 ft.


July 2015 TxDOT 35

Click here

or Edit: Copy Girder Properties

Verify the beam design works for the other beams.

By coping the girder design to the other girders and

reviewing the summary report for the critical beams.

In this case, check the exterior beam and the center

beam.






Select the beam or beams

you would like to copy

the design to.

Click to copy the design

to a different beam.


July 2015 TxDOT 36

STEP 7 - OUTPUT THE TEXT DATA FOR THE DETAIL SHEET (IBND, IGND, ETC.)

Click File:

Export:

TxDOT CAD Data


July 2015 TxDOT 37







July 2015 TxDOT 38

Selection a location and

file name. The file will

save as a *.txt file. This

file can then be imported

into Microstation.


July 2015 TxDOT 39

The process has

completed. Click OK.


July 2015 TxDOT 40

This is what the output

looks like.


July 2015 TxDOT 41

Appendix B


July 2015 TxDOT 42

METHOD FOR DEVELOPING NON STANDARD STRAND PATTERN

Select a Beam and Run

the Preliminary Girder

Designer.

Click

Then Click


July 2015 TxDOT 43

Accept the Design.

Notice f’ci is greater

than 5.5 ksi.


July 2015 TxDOT 44

The program notifies you if

the threshold is exceeded.

You can click on the

Exclamation Point to view

the value exceeded.


July 2015 TxDOT 45

Run the TxDOT Summary

Report.

At ½” diameter, there are a

significant number of

strands. Try 0.6” strands to

reduce the number of

strands.

Close the report.


July 2015 TxDOT 46

Click here

or Edit: Girder







July 2015 TxDOT 47

Change to

Grade 270 Low Relaxation 0.6”

Click OK

Then Run the Preliminary

Girder Designer


July 2015 TxDOT 48

Accept the Design.

Notice f’ci is greater

than 5.5 ksi.


July 2015 TxDOT 49

Run the TxDOT Summary

Report.

There are significantly

fewer strands, but the

release strength is higher.


July 2015 TxDOT 50

Scroll Down to the Stress

Checks.

Casting Yard Stage

controls the release

strength.

The program provides you

with the minimum release

strength required.

Edit the Girder to reduce

the release strength.


July 2015 TxDOT 51

Click here

or Edit: Girder






Click here

or Edit: Girder


July 2015 TxDOT 52

Click: Strands Tab

Change to

Number of Harped and Number

of Straight Strands


July 2015 TxDOT 53

The simplest way to develop

a non standard strand pattern

is by shifting stands from

straight strands to harped

strands.

To reduce the release strength

required for a given number

of strands, click the arrows

next to the numbers to reduce

the number if straight strands

by 2 and increase the number

of harped strands by 2.


July 2015 TxDOT 54

Click OK


July 2015 TxDOT 55

The program will

automatically update the

report for the new values.


July 2015 TxDOT 56

The release strength

requirement has been

reduced.

Edit Girder to reduce the

release strength.


July 2015 TxDOT 57

Under the General Tab,

modify the release strength.

Click OK.


July 2015 TxDOT 58

The program automatically

updated.

Scroll up to check the

Girder Design.


July 2015 TxDOT 59

Check this section to see if the

other checks are successful.

The release strength has been

reduced, but is still above 5.5 ksi.

Keep switching straight strands to

harped strands until you have

reduced the release strength to

below 5.5 ksi or as much as

possible without raising the final

strength to above 8.5 ksi.


July 2015 TxDOT 60

For this bridge, the final strand

arrangement is shown.


July 2015 TxDOT 61

This strand arrangement reduced

the release strength to 5.5 ksi.

What did it do to the final

strength? Check the report.


July 2015 TxDOT 62

We are good here.


July 2015 TxDOT 63


Specification Check Summary.

Tensile Stress fails. Scroll down

to get to the Tensile Stress Check.


July 2015 TxDOT 64

Final strength needs to be 7.8 ksi.

Edit Girder to change this value.


July 2015 TxDOT 65

Under the General Tab,

modify the final strength.

Click OK.


July 2015 TxDOT 66

The program automatically

updated the report.


Girder Design.


July 2015 TxDOT 67

Everything looks good here.

The specification check is

good.

The release strength is at

5.5 ksi.

The final strength is below

8.5 ksi.


July 2015 TxDOT 68

Click here

or View: Girder View

To strand arrangement


July 2015 TxDOT 69


July 2015 TxDOT 70


July 2015 TxDOT 71

This is how a non standard

strand is report on the

IGND.

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